When servicing valve assembly, inspect valve seats,
valve stems, valve faces, and valve stem ends for pits,
burn marks, or other signs of abnormal wear.

NOTE: The technician should reference the

appropriate illustration and/or photograph for the
model being serviced.

NOTE: Whenever a valve is out of tolerance, it

must be replaced.

Cleaning/Inspecting Valve Cover

NOTE: If the valve cover cannot be trued, the

cylinder head assembly must be replaced.

1. Wash the valve cover in parts-cleaning solvent.

2. Place the valve cover on the Surface Plate (p/n

0644-016) covered with #400 grit wet-or-dry
sandpaper. Using light pressure, move the valve
cover in a figure eight motion. Inspect the sealing
surface for any indication of high spots. A high spot
can be noted by a bright metallic finish. Correct any
high spots before assembly by continuing to move
the valve cover in a figure eight motion until a
uniform bright metallic finish is attained.

Do not remove an excessive amount of the
sealing surface or damage to the camshaft will
result. Always check camshaft clearance when
resurfacing the valve cover.

! CAUTION

3-154

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-770

CC385D

Fig. 3-771

CC130D

Water or parts-cleaning solvent must be used in
conjunction with the wet-or-dry sandpaper or
damage to the sealing surface may result.

Removing Valves

NOTE: Keep all valves and valve components as

a set. Note the original location of each valve set for
use during installation. Return each valve set to its
original location during installation.

1. Using a valve spring compressor, compress the

valve springs and remove the valve cotters. Account
for an upper spring retainer.

Fig. 3-772

CC391D

Fig. 3-773

CC132D

2. Remove the valve seal and the lower remaining

spring seat. Discard the valve seal.

Fig. 3-774

CC134D

! CAUTION

3-155

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-775

CC136D

NOTE: The valve seals must be replaced.

3. Remove the valve springs; then invert the cylinder

head and remove the valves.

Measuring Valve Stem Runout

1. Support each valve stem end with the V Blocks (p/n

0644-022); then check the valve stem runout using
a dial indicator.

Fig. 3-776

ATV1082

2. Maximum runout is 0.05 mm (0.002 in.).

Measuring Valve Stem
Outside Diameter

1. Using a micrometer, measure the valve stem

diameter.

2. Acceptable diameter range (intake valve) is

5.475-5.490 mm (0.2156-0.2161 in.) for the
250/300 cc and 4.975 - 4.990 mm (0.1959 - 0.1965
in.) for the 400/500 cc.

3. Acceptable diameter range (exhaust valve) is

5.455-5.470 mm (0.2148-0.2154 in.) for the
250/300 cc and 4.955 - 4.970 mm (0.1951 - 0.1957
in.) for the 400/500 cc.

Measuring Valve Face/Seat Width

1. Using a micrometer, measure the width of the valve

face.

Fig. 3-777

ATV1004

2. Acceptable width range is 0.9-1.1 mm (0.035-0.043

in.).

Measuring Valve Face Radial Runout

1. Mount a dial indicator on the surface plate; then

place the valve stem on a set of V blocks.

2. Position the dial indicator contact point on the

outside edge of the valve face; then zero the
indicator.

Fig. 3-778

ATV1082A

3. Rotate the valve in the V blocks.

4. Maximum runout is 0.03 mm (0.001 in.).

Measuring Valve Guide/Valve Stem
Deflection (Wobble Method)

1. Mount a dial indicator and base on the surface plate;

then place the cylinder head on the surface plate.

2. Install the valve into the cylinder head; then

position the dial indicator contact point against the
outside edge of the valve face. Zero the indicator.

3-156

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-779

CC131D

3. Push the valve from side to side; then from top to

bottom.

4. Maximum “wobble” deflection is 0.35 mm (0.014

in.).

Measuring Valve Guides
(Inside Diameter)

1. Insert a snap gauge 1/2 way down into each valve

guide bore; then remove the gauge and measure it
with a micrometer.

2. Acceptable inside diameter range is 5.500-5.512

mm (0.2165-0.2170 in.) for the 250/300 cc and
5.000 - 5.012 mm (0.1969 - 0.1973 in.) for the
400/500 cc.

3. If a valve guide is out of tolerance, it must be

replaced.

Replacing Valve Guide

NOTE: If a valve guide is worn or damaged, it must

be replaced.

1. If a valve guide needs replacing, insert a valve guide

remover into the valve seat side of the valve guide.
Using a hammer, gently drive the valve guide out of
the cylinder head.

Fig. 3-780

CC393D

Fig. 3-781

CC137D

2. Using the Standard Valve Guide Reamer (p/n

0444-017), remove any burrs or tight areas from the
valve guide journals.

Fig. 3-782

CC142D

3. To install a valve guide, use a valve guide installer

and gently drive a valve guide with a retaining clip
into the bore from the valve spring side until the
retaining clip just contacts the cylinder head.

Fig. 3-783

CC143D

4. After installing the guide, use the standard valve

guide reamer to remove all burrs and tight areas that
may remain in each valve guide.

3-157

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-784

CC394D

Fig. 3-785

CC138D

ATV-0107

Grinding Valve Seats

NOTE: If the valve seat is beyond servicing, the

cylinder head must be replaced.

1. Insert an exhaust valve seat pilot shaft into an

exhaust valve guide. Slide an exhaust valve seat
grinding tool onto the pilot shaft; then using light
pressure on a driver handle and a deep socket, grind
the exhaust valve seat until within specifications.

Fig. 3-786

CC396D

NOTE: On the 400/500 cc, repeat procedure on the

remaining exhaust valve.

Fig. 3-787

CC139D

2. Insert an intake valve seat pilot shaft into one of the

intake valve guides. Slide the intake valve seat
grinding tool onto the pilot shaft; then using light
pressure on a driver handle and a deep socket, grind
the intake valve seat until within specifications.

Valve Seat/Guide Servicing Flow Chart

3-158

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-788

CC395D

NOTE: On the 400/500 cc, repeat procedure on the

remaining intake valve.

Fig. 3-789

CC140D

Lapping Valves

NOTE: Do not grind the valves. If a valve is

damaged, it must be replaced.

1. Remove all carbon from the valves.

2. Lubricate each valve stem with light oil; then apply

a small amount of valve lapping compound to the
entire seating face of each valve.

3. Attach the suction cup of a valve lapping tool to the

head of the valve.

4. Rotate the valve until the valve and seat are evenly

polished.

5. Clean all compound residue from the valve and

seat.

Measuring Rocker Arms
(Inside Diameter)

1. Using a dial calipers, measure the inside diameter

of the rocker arm.

2. Acceptable inside diameter range is 12.000-12.018

mm (0.472-0.473 in.).

Measuring Rocker Arm Shafts
(Outside Diameter)

1. Using a micrometer, measure the outside diameter

of the rocker arm shaft.

2. A c c e p t a b l e

o u t s i d e

d i a m e t e r

r a n g e

i s

11.977-11.995 mm (0.4715-0.4722 in.) for the
250/300 cc and 11.973-11.984 mm (0.4714-0.4718
in.) for the 400/500 cc.

Installing Valves

1. Apply grease to the inside surface of the valve seals;

then place a lower spring seat and valve guide seal
over each valve guide.

Fig. 3-790

CC144D

2. Insert each valve into its original valve location.

3. Install the valve springs with the painted end of the

spring facing away from the cylinder head.

NOTE: If the painted end is not visible, install the

ends of the springs with the closest coils toward the
head.

Fig. 3-791

ATV1011

NOTE: The 250 cc has only the larger spring.

4. Place a spring retainer over the valve springs; then

using the valve spring compressor, compress the
valve springs and install the valve cotters.

3-159

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-792

CC391D

Fig. 3-793

CC132D

PISTON ASSEMBLY

NOTE: Whenever a piston, rings, or pins are out of

tolerance, they must be replaced.

Cleaning/Inspecting Piston

1. Using a non-metallic carbon removal tool, remove

any carbon buildup from the dome of the piston.

2. Inspect the piston for cracks in the piston pin, dome,

and skirt areas.

3. Inspect the piston for seizure marks or scuffing.

Repair with #400 grit wet-or-dry sandpaper and
water or honing oil.

Fig. 3-794

AN135

NOTE: If scuffing or seizure marks are too deep to

correct with the sandpaper, replace the piston.

4. Inspect the perimeter of each piston for signs of

excessive “blowby.” Excessive “blowby” indicates
worn piston rings or an out-of-round cylinder.

Removing Piston Rings

1. Starting with the top ring, slide one end of the ring

out of the ring-groove.

Fig. 3-795

CC400D

2. Remove each ring by working it toward the dome of

the piston while rotating it out of the groove.

NOTE: If the existing rings will not be replaced

with new ones, note the location of each ring for
proper installation. When installing new rings,
install as a complete set only.

Cleaning/Inspecting Piston Rings

1. Take an old piston ring and snap it into two pieces;

then grind the end of the old ring to a 45° angle and
to a sharp edge.

2. Using the sharpened ring as a tool, clean carbon

from the ring-grooves. Be sure to position the ring
with its tapered side up.

Improper cleaning of the ring-grooves by the use
of the wrong type of ring-groove cleaner will
result in severe damage to the piston.

Measuring Piston-Ring End Gap

1. Place each piston ring in the wear portion of the

cylinder. Use the piston to position each ring
squarely in the cylinder.

! CAUTION

3-160

-------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Using a feeler gauge, measure each piston-ring end

gap. Acceptable ring end gap must be a maximum
0.70 mm (0.028 in.) 1st ring and 1.0 mm (0.039 in.)
2nd ring for the 250/300 cc, a maximum 0.50 mm
(0.020 in.) both rings for the 400 cc, and a
maximum 0.70 mm (0.028 in.) both rings for the
500 cc.

Fig. 3-796

CC386D

Fig. 3-797

CC280D

Measuring Piston Pin (Outside
Diameter) and Piston-Pin Bore

1. Measure the piston pin outside diameter at each end

and in the center. If measurement is less than 16.980
mm (0.6685 in.) for the 250/300 cc, 20.98 mm
(0.826 in.) for the 400 cc, and 22.98 mm (0.905 in.)
for the 500 cc, the piston pin must be replaced.

Fig. 3-798

ATV1070

2. Insert an inside dial indicator into the piston-pin

bore. The diameter must be a maximum 17.030 mm
(0.6705 in.) for the 250/300 cc, 21.03 mm (0.828
in.) for the 400 cc, and 23.03 mm (0.907 in.) for the
500 cc. Take two measurements to ensure accuracy.

Fig. 3-799

ATV1069

Measuring Piston Skirt/
Cylinder Clearance

1. Measure the cylinder front to back in six places.

Fig. 3-800

CC397D

2. Measure the corresponding piston diameter at a

point 18 mm (0.71 in.) for the 250/300 cc and 15
mm (0.60 in.) for the 400/500 cc above the piston
skirt at a right angle to the piston-pin bore. Subtract
this measurement from the measurement in step 1.
The difference (clearance) must be a maximum
0.12 mm (0.0047 in.) for the 250/300 cc and within
a range of 0.045-0.120 mm (0.0018-0.0047 in.) for
the 400 cc or 0.038-0.076 mm (0.0015-0.0030 in.)
for the 500 cc.

3-161

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Installing Piston Rings

1. Install a thin ring, corrugated ring, and thin ring in

the bottom groove of the piston. Stagger the gaps of
the upper and lower thin rings.

Fig. 3-801

ATV-1085

2. Install the middle and upper rings so the letter on

the top surface of each ring faces the dome of the
piston. Rotate the rings until the ring gaps are on
directly opposite sides of the piston.

Fig. 3-802

726-306A

Incorrect installation of the piston rings will
result in engine damage.

CYLINDER /CYLINDER HEAD
ASSEMBLY

NOTE: If the cylinder/cylinder head assembly

cannot be trued, they must be replaced.

Cleaning/Inspecting Cylinder Head

The cylinder head studs must be removed for
this procedure.

1. Using a non-metallic carbon removal tool, remove

any carbon buildup from the combustion chamber
being careful not to nick, scrape, or damage the
combustion chamber or the sealing surface.

2. Inspect the spark plug hole for any damaged

threads. Repair damaged threads using a “heli-coil”
insert.

3. Place the cylinder head on the surface plate covered

with #400 grit wet-or-dry sandpaper. Using light
pressure, move the cylinder head in a figure eight
motion. Inspect the sealing surface for any
indication of high spots. A high spot can be noted
by a bright metallic finish. Correct any high spots
before assembly by continuing to move the cylinder
head in a figure eight motion until a uniform bright
metallic finish is attained.

Water or parts-cleaning solvent must be used in
conjunction with the wet-or-dry sandpaper or
damage to the sealing surface may result.

Fig. 3-803

CC387D

Fig. 3-804

CC128D

! CAUTION

3-162

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Measuring Cylinder Head Distortion

1. Remove any carbon buildup in the combustion

chamber.

2. Lay a straightedge across the cylinder head; then

using a feeler gauge, check the distortion factor
between the head and the straightedge.

3. Maximum distortion is 0.05 mm (0.002 in.).

Fig. 3-805

CC388D

Fig. 3-806

CC141D

Cleaning/Inspecting Cylinder

1. Wash the cylinder in parts-cleaning solvent.

2. Inspect the cylinder for pitting, scoring, scuffing,

warpage, and corrosion. If marks are found, repair
the surface using a cylinder hone (see Honing
Cylinder in this sub-section).

3. Place the cylinder on the surface plate covered with

#400 grit wet-or-dry sandpaper. Using light
pressure, move the cylinder in a figure eight
motion. Inspect the sealing surface for any
indication of high spots. A high spot can be noted
by a bright metallic finish. Correct any high spots
before assembly by continuing to move the cylinder
in a figure eight motion until a uniform bright
metallic finish is attained.

Water or parts-cleaning solvent must be used in
conjunction with the wet-or-dry sandpaper or
damage to the sealing surface may result.

Fig. 3-807

CC389D

Fig. 3-808

CC129D

Inspecting Cam Chain Guide

1. Inspect cam chain guide for cuts, tears, breaks, or

chips.

2. If the chain guide is damaged, it must be replaced.

Honing Cylinder

1. Using a slide gauge and a dial indicator or a snap

gauge, measure the cylinder bore diameter in three
locations from top to bottom and again from top to
bottom at 90° from the first measurements for a
t o t a l o f si x m e a s u r e m e n t s . T h e t r u e n e s s
(out-of-roundness) is the difference between the
highest and lowest reading. Maximum trueness
(out-of-roundness) must be 0.05 mm (0.002 in.).

! CAUTION

3-163

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-809

CC397D

Fig. 3-810

CC127D

2. Wash the cylinder in parts-cleaning solvent.

3. Inspect the cylinder for pitting, scoring, scuffing,

and corrosion. If marks are found, repair the surface
using a rigid cylinder hone.

NOTE: To produce the proper 60° cross-hatch

pattern, use a low RPM drill (600 RPM) at the rate of
30 strokes per minute. If honing oil is not available,
use a lightweight petroleum-based oil. Thoroughly
clean cylinder after honing using soap and hot
water. Dry with compressed air; then immediately
apply oil to the cylinder bore. If the bore is severely
damaged or gouged, replace the cylinder.

Fig. 3-811

CC390D

Fig. 3-812

CC321D

4. If any measurement exceeds the limit, hone the

cylinder and install an oversized piston or replace
the cylinder.

NOTE: Oversized piston and rings are available.

The oversized piston and rings are marked for
identification.

Fig. 3-813

ATV-1068

Measuring Camshaft Runout

NOTE: If the crankshaft is out of tolerance, it must

be replaced.

1. Place the camshaft on a set of V blocks; then

position the dial indicator contact point against the
shaft and zero the indicator.

3-164

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-814

CC398D

Fig. 3-815

CC283D

2. Rotate the camshaft and note runout; maximum

tolerance is 0.10 mm (0.004 in.).

Measuring Camshaft Lobe Height

1. Using a calipers, measure each cam lobe height.

Fig. 3-816

ATV1013A

2. On the 250/300 cc, the intake lobe height must be a

minimum 33.820 mm (1.331 in.); exhaust lobe
height must be a minimum 33.490 mm (1.318 in.).
On the 400/500 cc, intake lobe height must be a
minimum 33.150 mm (1.305 in.); exhaust lobe
height must be a minimum 33.220 mm (1.308 in.).

Inspecting Camshaft Bearing Journal

1. Inspect the bearing journal for scoring, seizure

marks, or pitting.

2. If excessive scoring, seizure marks, or pitting is

found, the cylinder head assembly must be
replaced.

Measuring Camshaft to
Cylinder Head Clearance

1. Remove the adjuster screws and jam nuts.

Fig. 3-817

CC407D

Fig. 3-818

CC005D

2. Place a strip of plasti-gauge in each of the camshaft

lands in the cylinder head.

3. Place the valve cover on the cylinder head and

secure with the valve cover cap screws. Tighten
securely.

N OT E : D o not rot ate the cam shaft when

measuring clearance.

4. Remove the cap screws securing the valve cover to

the cylinder; then remove the valve cover and
camshaft.

3-165

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-819

CC367D

Fig. 3-820

CC003D

5. Match the width of the plasti-gauge with the chart

found on the plasti-gauge packaging to determine
camshaft to cylinder head and valve cover
clearance.

Fig. 3-821

CC145D

6. If clearance is excessive, measure the journals of

the camshaft.

Fig. 3-822

CC399D

Fig. 3-823

CC287D

NOTE: If the journals are worn, replace the

camshaft; then measure the clearance again. If it is
still out of tolerance, replace the cylinder head.

Inspecting Camshaft Spring/Drive Pin
(400/500 cc)

1. Inspect the spring and drive pin for damage.

Fig. 3-824

CC304D

3-166

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-825

CC306D

Fig. 3-826

CC308D

2. If damaged, the camshaft must be replaced.

Servicing Left-Side

Components

RECOIL STARTER

NOTE: The technician should reference the

appropriate illustration and/or photo for the model
being serviced.

Fig. 3-827

0733-751

Fig. 3-828

0732-309

Fig. 3-829

0735-614

! WARNING

Always wear safety glasses when servicing the
recoil starter.

KEY

1. Recoil Starter Assy
2. Reel
3. Ratchet Assy
4. Spring
5. Nut
6. Rope Assy
7. Gasket
8. Cap Screw
9. Gasket

10. Starter Cap
11. Nut
12. Lock Washer

250/300 cc

KEY

1. Recoil Starter Assy
2. Reel
3. Ratchet
4. Pin
5. Spring
6. Spring
7. Shaft
8. Spring Cover
9. Friction Plate

10. Ratchet Guide
11. Nut
12. Rope Assy
13. Gasket
14. Bolt
15. Starter Cup
16. Nut
17. O-Ring

400/500 cc
Manual Transmission

KEY

1. Recoil Starter Assy
2. Reel
3. Ratchet Assy
4. Spiral Spring
5. Nut
6. Rope Assy
7. Gasket
8. Cap Screw
9. Starter Cup

10. Nut
11. O-Ring
12. Spacer
13. Bearing
14. O-Ring
15. Oil Seal

Automatic Transmission

3-167

Click Here to Continue

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Removing/Disassembling

1. Remove the cap screws securing the recoil starter

assembly to the left-side cover; then remove the
starter noting (on the 250/300 cc) the location of the
single washer closest to the center of the crankcase.
Account for a gasket.

Fig. 3-830

CC412D

Fig. 3-831

CC039D

! WARNING

During the disassembly procedure, continuous
downward pressure must be exerted on the reel
so it does not accidentally disengage and cause
injury.

2. Rotate the reel counterclockwise until the notch of

the reel is near the rope guide in the case. Guide the
rope into the notch and slowly allow the reel to
retract until all spiral spring tension is released.

Fig. 3-832

B600D

During the disassembly procedure, make sure
all spring tension is released before continuing.

3. Remove the nut.

Fig. 3-833

B601D

4. Slowly release the friction plate and lift the plate

with ratchet guide free of the recoil housing; then
remove the ratchet guide from the friction plate.

Fig. 3-834

B602D

5. Remove the spring, collar, and friction spring.

Fig. 3-835

B603D

6. Remove the ratchet.

! CAUTION

3-168

Click Here to Go Back

-------------------------------------------------------------------------------------------------------------------------------------------------------------

Fig. 3-836

B604D

7. Carefully lift the recoil free of the case making sure

the spring does not accidentally disengage from the
case.

Fig. 3-837

B605D

! WARNING

Care must be taken when lifting the recoil free of
the case. Wear safety glasses to avoid injury.

8. Remove the protective cover from the starter handle

and pull the rope out of the handle; then untie the
knot in the rope and remove the handle.

NOTE: Do not remove the spiral spring unless

replacement is necessary. It should be visually
inspected in place to save time. If replacement is
necessary, follow steps 9-10.

9. Remove the spring from the housing by lifting the

spring end up and out. Hold the remainder of the
spring with thumbs and alternately release each
thumb to allow the spring to gradually release from
the housing.

10. Unwind the rope from the reel and remove the rope.

Cleaning and Inspecting

NOTE: Whenever a part is worn excessively,

cracked, or damaged in any way, replacement is
necessary.

1. Clean all components.

2. Inspect the springs and ratchet for wear or damage.

3. Inspect the reel and housing for cracks or damage.

4. Inspect the shaft for wear, cracks, or damage.

5. Inspect the rope for breaks or fraying.

6. Inspect the spiral spring for cracks, crystallization,

or abnormal bends.

7. Inspect the handle for damage, cracks, or

deterioration.

Assembling/Installing

1. If removed, insert the spring into the housing with

the outer end of the spring around the mounting lug
in the housing; then wind it in a counterclockwise
direction until the complete spring is installed.

NOTE: The recoil spring must seat evenly in the

recoil case.

Fig. 3-838

B606D

2. Insert the rope through the hole in the reel and tie a

knot in the end; then wrap the rope counter-
clockwise around the reel leaving approximately 50
cm (20 in.) of rope free of the reel.

3. Apply low-temperature grease to the spring and

hub.

4. Thread the end of the rope through the guide hole

of the housing; then thread the rope through the
handle and secure it with a double knot. Install the
protective cover into the handle.

5. Align the inner hook of the spring with the notch in

the reel.

3-169

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Content .. 12 13 14 15 ..